| Around the 'Bolt...
Search the 'Bolt - more than 100,000 pages of info. Start here if you're hunting!
More than 38,400 registered
from around the world talking old trucks, and sharing technical help.
Gallery More than 3,140 old truck stories with photos from Stovebolters worldwide! More in our DITY Gallery.
Helpful tips on truck restoration, identification, preservation; project stories, Build Blogs and Stovebolt histories.
Find out who's doing what, where and when! See who else is in your neighborhood with an old truck.
FREE Classified ads for trucks, parts, truck citings, eBay / Craigslist, Hauling Board.
Nothing new under the sun ... got some good Frequently Asked Questions here, and will probably have more!
Sagas, Feature Stories and some stuff we've
done here and there and don't know where else to put it!
'Bolter wear, calendars, bling and other goodies!
About Us, Contacting Us, Stovebolt Supporters,
and other pertinent administrivia.
Return to the home page
Other Radio Tech Tips:
No parts of this site, its contents, photos or graphics may be used without permission.
Copyright © 1995-2021
Your Stovebolt is just a joy to drive. You've got heads turning and thumbs going up everywhere you drive. There's room for the whole family and the dogs. You've been hauling all kinds of neat stuff in the bed. Life is good ... but (in the old tradition of "it's never really finished") if only it had a decent radio ...
Well, here we go, Stovebolters! Here are some handy tips from Gary Tayman who specializes in collector car audio, radio, and clocks for antique and vintage vehicles (cars and trucks). It seems there's a lot of interest in sound systems but not much knowledge -- so we hope this will be a great help!
to determine what is wrong and why the radio doesn't work? Well, it is not
always the radio that is broken. And if it proves to be your radio after all, Gary
has some very good suggestions on what to look for and where to go.
Troubleshooting your radio
A non-working radio isn't
always what it seems. The real culprit could be anything from a bad antenna
cable to incorrect spark plug wires. The following are some troubleshooting tips
to help you pinpoint the problem -- to either the radio itself or an external
No sign of life:
(No hiss, no pop, no static, nothing but a dead radio)
- I know it's tempting, but
ignore the dial lamp. On many cars, the lamp is on a different circuit from the
radio. You can pull the fuse to the radio and the lamp will still light in many
- With a voltmeter, or one
of those cute light-up test probes, check the power lead to the radio. Don't
forget to turn the key on to ACC! Check for 6 or 12 volts between the power lead
and the metal dash (or car frame). If you don't know which lead is for power, it
can't hurt to check every lead -- one of them should have 6 or 12 volts when the
key is on.
- So you have power to the
radio, but you still don't hear anything? Check the speaker. With an ohmmeter, or
flashlight battery if you don't have all this tech stuff around the house, touch
the probes or battery to the speaker leads. (On some cars there is only one
lead; touch the other probe to the car frame.) Just like that bowl of breakfast
cereal, you should hear some sort of faint snap, crackle, and pop from the
speaker as you make contact. If you don't, the radio may be playing its heart
out to a dead speaker.
By the way, in case you care, the ohmmeter should read
about 3 to 10 ohms.
Weak or distorted
sound: (You hear something, but it's not right)
- Your speaker may pass the
snap, crackle, pop test, but if the cone is warped or torn, it won't sound very
good. Try another speaker.
- If reception is poor, try
another antenna. Connect it to the radio and hold it out the window. Ignore the
people who are looking at you funny; remember they don't have a classic vehicle like
you do. Try out the radio -- you should get at least a handful of stations.
- Don't overlook the antenna
trimmer. This is a small adjustment that is usually located near the antenna
socket. On some radios it is found behind the tuning knob. To adjust, tune to a
weak station between 1200 and 1400 AM. Adjust this (may require a screwdriver)
for strongest reception.
Loud buzzing sounds, or
(You can't hear the music for all the noise)
- If the radio sounds fine
before you start the engine, the problem is under the hood. Make sure you have
resistor spark plug cables -- the reason for the resistance is radio reception.
Also, make sure you have the proper condensers on the generator/alternator
and/or voltage regulator.
- Here's where it gets fun
-- your car's electrical system is old enough to retire. Connectors are
corroded, switches are dirty, and these defects can manifest themselves in the
form of radio interference. For example, let's say you're listening to your
favorite doo-wop as you make a left turn. Flick the turn signal and the radio
goes pop-pa-pop-pa-pop! There is a bad connection somewhere between the battery
and the turn signal flasher, and the line voltage fluctuations are being picked
up by the radio. You can verify this with your voltmeter -- assuming you have
one. If you measure between the battery and the turn signal flasher, you should
measure zero. But with a bad connection you may measure anywhere from half a
volt to 4 or 5 volts! You can use that voltmeter to isolate the bad connection.
Often the ignition switch itself is the culprit; don't overlook it.
- If you're doing all this
in your garage, keep in mind that shop lights, air conditioners, and all sorts
of other garage-type appliances can be a source of radio noise. Take your car
down the street and see if the noise goes away -- or find a portable AM radio
and see if it makes the same noises in the garage. If you do this, turn the car
radio off. Otherwise both radios will squeal -- or did you know this? If you put
two AM radios near each other, they will both make a squealing noise that will
change in pitch if you tune either of them.
- On older tube type sets, a
faint hum from the vibrator is normal. But if you hear a loud hum or buzz
through the speaker, wrap it up and send it for service -- your filters have
gone bad, a common problem with old sets which have sat around unused.
- When bench testing a
radio, make sure the power supply is connected properly. Many people find the 6
or 12 volt wire, but connect the minus lead to another wire. Connect the minus
lead to ground. For positive ground vehicles, connect the red lead to ground and the
black lead to the power wire.
- Back in the olden days,
vibrators failed left and right, and were user replaceable. Today you can buy a
solid state replacement which is far better, but I don't recommend replacing it
yourself. The reason is not because I'd rather you have me do it; it's because
there are other components that, after 50 years, are usually bad and will blow
even the best of vibrators. The worst offender is called a buffer -- it's a
capacitor placed across the transformer secondary, designed to withstand voltage
spikes of up to 1,600 volts. If the buffer is original, sight unseen I could bet
you it's bad, and I'd win. If you're handy with a soldering iron, you have my
permission to replace the buffer (make sure it's rated at least 1600 volts).
While you're at it, replace every wax-paper capacitor in the set, and check the
rectifier. Your radio will feel much better, and the vibrator should then be
safe in its new home.
- Sometimes a user will buy
all new tubes, with hopes of avoiding a repair bill. I'm going to save you a
tube bill by saying that tubes almost never cause a radio to fail. One or two
tubes may be weak, but this does not shut down the radio -- something else is
wrong. Sometimes I get a radio that "worked poorly before, but after
putting in all new tubes it doesn't play at all." Invariably the tubes are
in the wrong sockets. No, they are not all the same. Also, never tighten the
adjustment screws on the chassis, circuit board or IF cans. These are for
alignment -- they don't tighten anything. Yes, people have done this . . .
- Finally, be careful where
you send it for repair. Your local TV repair shop quit servicing your 50
year-old radio 45 years ago. They don't stock the parts or have the literature,
and many have never worked on tube-type devices. On the other hand, there are
nice folks, that I would like to include myself in, that specialize in vintage
radio equipment, either as a hobby or as a business. We have the older
literature, we have sources for many of the parts, we talk shop to each other,
and we even buy test equipment -- much of my literature and test equipment came
from another dealer in Clearwater. There really are resources for rare vintage
parts, although sometimes it takes awhile to locate certain special items. But
the good news is that there is a community of people who specialize in this
older equipment, that can take care of you. If you've determined that your radio
needs attention, please let me know -- I'm at your service.
If these tips don't cover it all for you ... or you're hopelessly lost, Gary's got another Tech Tip for us on Shopping for a Used Radio. A big thanks to Gary for this Tech Tip and a big thanks to Stovebolter Richard "Richard2005" Rosielle for helping us get it together.~~ Editor
|Be sure to check out our extensive Forums discussions -- from General Truck talk, Electrical Bay, Big Bolts, Panels and Burbs, Engine and Driveline, Paint and Body, Interiors, Tool Chest -- The Stovebolt Collective can help in your quest and walk you through the mire and magic of working with old iron!
Working on my old truck reminds me of fudge -- sometimes it's sooo sweet.
Other times it drives me nuts!